There are lots of lolcat builders out there, but this is the only one I've used: http://builder.cheezburger.com/Builder
You're on your own for legally available images, though. I think the community consensus is that it doesn't matter because parody or whatever, which is not a legitimate legal defense, but I don't think anybody's been sued yet.
The builder seems great. Thousands of cat pictures!


You know the drill - If it's worth saying, but not worth its own post (even in Discussion), then it goes here.